docs: def parse_logout_request(self, message_text):
          '''
          Parse the contents of a CAS `LogoutRequest` XML message.
  
          ::
  
              >>> from cas_client import CASClient
              >>> client = CASClient('https://logmein.com')
              >>> message_text = """
              ... <samlp:LogoutRequest
              ...     xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"
              ...     xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion"
              ...     ID="935a2d0c-4026-481e-be3d-20a1b2cdd553"
              ...     Version="2.0"
              ...     IssueInstant="2016-04-08 00:40:55 +0000">
              ...     <saml:NameID>@NOT_USED@</saml:NameID>
              ...     <samlp:SessionIndex>ST-14600760351898-0B3lSFt2jOWSbgQ377B4CtbD9uq0MXR9kG23vAuH</samlp:SessionIndex>
              ... </samlp:LogoutRequest>
              ... """
              >>> parsed_message = client.parse_logout_request(message_text)
              >>> import pprint
              >>> pprint.pprint(parsed_message)
              {'ID': '935a2d0c-4026-481e-be3d-20a1b2cdd553',
               'IssueInstant': '2016-04-08 00:40:55 +0000',
               'Version': '2.0',
               'session_index': 'ST-14600760351898-0B3lSFt2jOWSbgQ377B4CtbD9uq0MXR9kG23vAuH',
               'xmlns:saml': 'urn:oasis:names:tc:SAML:2.0:assertion',
               'xmlns:samlp': 'urn:oasis:names:tc:SAML:2.0:protocol'}
  
          '''
          result = {}
          xml_document = parseString(message_text)
          for node in xml_document.getElementsByTagName('saml:NameId'):
              for child in node.childNodes:
                  if child.nodeType == child.TEXT_NODE:
                      result['name_id'] = child.nodeValue.strip()
          for node in xml_document.getElementsByTagName('samlp:SessionIndex'):
              for child in node.childNodes:
                  if child.nodeType == child.TEXT_NODE:
                      result['session_index'] = str(child.nodeValue.strip())
          for key in xml_document.documentElement.attributes.keys():
              result[str(key)] = str(xml_document.documentElement.getAttribute(key))
          logging.debug('[CAS] LogoutRequest:\n{}'.format(
              json.dumps(result, sort_keys=True, indent=4, separators=[',', ': ']),
              ))
          return result